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Intruder detector
Page 88
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A security alarm system developed by AFA-Minerva (EMI) is said to obviate spurious alarms caused by inanimate objects flapping or swinging within their range such as curtains, doors, windows, shutters or signs.
A sonar detector can discriminate between different types of motion within its range. Its electronic memory enables it to ignore typical wavering movements that often trigger off security systems unnecessarily, but it identifies the approach_ of an intruder and sounds a warning.
Known as the Fidela 3, the equipment is designed to detect intruders inside premises ranging from shops and offices, industrial and commercial buildings to museums and art galleries. Measuring 11 in. long, 7in. wide and 2-lin. deep, the device can be attached to most types of vertical surface. Different patterns of protective field can be provided to meet specific situations.
Ultrasonic sound waves are emitted and the signals are interrogated after deflection from solid objects along their path. Change in frequency of these sound waves, caused by any movement within its field of operation, is monitored by the equipment's signal processing circuits.
The detector's basic range pattern is an egg-shaped zone of protection, nominally measuring 25ft long and 17ft at its widest point. This pattern can be easily adjusted to deflect to the right, left or downwards and be broadened to about 40ft wide with a corresponding reduction in range length to around 12ft.
The basic detector comprises a control sensor incorporating transmitting and receiving transducers, power supply, signal processing circuitry, standby battery and charger, alarm relay output and anti-tamper connections. The unit has a rocker switch and a light at its base to facilitate checks on operation.
Should an area requiring intruder protection exceed the limits of a single detector, the protective zone can be enlarged by the addition of two slave units. With an enclosure matching that of the control device, each of these units contains only transmitting and receiving transducers and is powered and controlled from the basic Fidela 3 module.
Made by: AFA-Minerva (EMI) Ltd, Security House, Grosvenor Road, Twickenham, Middx.